🧊 Cardioplegia – The Art of Myocardial Protection

Cardioplegia is the intentional and temporary arrest of the heart using a specially formulated solution, administered during cardiopulmonary bypass (CPB) to protect the myocardium during cardiac surgery.

The word cardioplegia literally means “heart paralysis”, and its primary aim is to reduce myocardial oxygen consumption (MVO₂) and prevent ischemic injury.

🧠 Why Cardioplegia?

During open-heart surgery:

• The heart must be still for precise surgical work.
• Aortic cross-clamping cuts off coronary perfusion → risk of ischemia.
• Cardioplegia allows electromechanical arrest, hypothermia, and oxygen substrate delivery → preserving cellular integrity.

🔹 Goals of Cardioplegia

• Achieve rapid diastolic cardiac arrest
• Provide myocardial hypothermia
• Prevent ischemia-reperfusion injury
• Reduce metabolic demands of myocardium
• Allow uniform distribution of nutrients and washout of metabolites

🧪 Components of Cardioplegia Solution

🌡️ Types of Cardioplegia

🔵 1. Based on Composition

• Crystalloid cardioplegia: Electrolyte + substrate solution (e.g., St. Thomas, Custodiol HTK)
• Blood cardioplegia: Autologous blood + additives (ratio 4:1 or 8:1); better oxygen-carrying capacity

🔵 2. Based on Temperature

• Cold (4–10°C) – Most common; reduces MVO₂ by 90–95%
• Tepid (28–32°C) – Less metabolic suppression but avoids cold-induced vasoconstriction
• Warm (normothermic, 37°C) – Delivers metabolic substrates actively (warm-blood cardioplegia)

🔵 3. Based on Delivery

• Antegrade – via aortic root into coronary ostia (most common)
• Retrograde – via coronary sinus (used in aortic insufficiency or obstructed coronaries)
• Ostial – directly into coronary ostia during aortic valve surgery
• Combined – antegrade + retrograde

🔵 4. Based on Dosing Strategy

• Intermittent – Every 15–20 mins, 600–1000 mL
• Continuous – Lower volumes, but continuous delivery

⚙️ Mechanism of Myocardial Arrest

• High K⁺ (20–30 mEq/L) depolarizes cell membrane.
• Sodium channels inactivate → No depolarization → Diastolic arrest
• Non coronary collateral flow washes out the cardioplegic solution therefore it has to be replenished in 20-30 mins.
• Cooling reduces ATP use, slows metabolism.

🧊 Custodiol (HTK Solution) – A Single-Dose Crystalloid Cardioplegia

• Low sodium, low calcium
• Histidine buffers pH
• Tryptophan stabilizes membranes
• Ketoglutarate aids ATP regeneration
• Used for prolonged arrest (up to 2–3 hours) in congenital and transplant surgeries

💡 Clinical Considerations for Anesthesiologists

Pre-CPB:

• Ensure ACT > 480s before initiating CPB and cardioplegia
• Monitor aortic root pressure during antegrade delivery
• Avoid LV distension with proper venting

During CPB:

• Monitor for arrhythmias, especially on rewarming and reperfusion
• Monitor temperature gradient (<10°C) between inflow and venous blood to prevent gas embolism
• Consider blood gas cardioplegia analysis if using blood cardioplegia
• Maintain myocardial temperature at 10–15°C (cold) or 28–32°C (tepid)

Post-CPB:

• Watch for return of sinus rhythm; pacing may be required
• Calcium supplementation post-CPB to restore contractility
• Reperfusion arrhythmias are common – manage with Mg²⁺ or lidocaine

❗ Complications of Cardioplegia

• Inadequate myocardial protection → myocardial stunning
• Electrolyte disturbances – Hyperkalemia, Hypocalcemia
• Myocardial edema due to excessive volume or poor venting
• Arrhythmias on rewarming or reperfusion
• Embolism if air entrainment or inadequate de-airing

🧠 Viva & MCQ Nuggets